Hormonal Regulation of Renal Ornithine Decarboxylase Activity in the Rat¹

Abstract

The regulation of the activity of the renal enzyme ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) was examined in the rat. In the intact animal adapted to a light/dark cycle of 14 hours and 10 hours, respectively, the level of renal ornithine decarboxylase activity was rhythmical and paralleled the diurnal rhythm in plasma corticosteroid concentration. Renal ornithine decarboxylase activity and plasma corticosterone were highest during the early hours of darkness and lowest during the hours of light. Following hypophysectomy, the level of renal ornithine decarboxylase activity declined rapidly and remained low and without a demonstrable diurnal rhythm. When pituitary hormone levels were temporarily restored in the hypophysectomized rat by the injection of pituitary extract, renal ornithine decarboxylase activity increased rapidly, reached a peak within 8 hours, and returned toward pre-injection levels by 12 hours. Exogenous growth hormone, ACTH and cortisol each increased renal ornithine decarboxylase activity in the hypophysectomized rat, with the highest levels of activity being achieved with growth hormone. Other pituitary hormones (FSH, LH, TSH and prolactin) were ineffective. After bilateral adrenalectomy, renal ornithine decarboxylase activity retained a rhythmical pattern similar to that observed in the intact rat, but the levels were increased. Growth hormone and cortisol increased renal ornitine decarboxylase activity in the adrenalectomized-hypophysectomized animal to the same extent as in the hypophysectomized animal, but ACTH was almost totally ineffective. These data suggest that the pituitary plays a major role in the regulation of renal ornithine decarboxylase activity in the rat, primarily through the rhythmical secretion of growth hormone and ACTH.

Compensatory Growth and Other Growth Responses of the Kidney

“…The effects of somatotropin of varying degrees of purity tend to correlate inversely with the estimates of CRG in the untreated. A marked enhanc ement of CRG but less than in normal controls is re ported in experiments in which relatively little CRG was found in untreated [24,166] and little or none in those with significant untreated CRG [359,422,425]. The latter conclusion is supported by the observation of near-nor mal CRG in mice with congenital deficiency of prolactin and thyro-and somatotropin [39,237],…”

“…The conflicting results might reflect varying degress of purity of extracts. The relative contribution of somatotropin alone to kidney size is measured by a K / B ratio 20% lower than normals in somatotropin-deficient mice [237], So matotropin, adrenocorticotropin and cortisol to a lesser extent, but not gonadotropins, thyrotropin or prolactin increased ornithine decarboxylase activity in hypophy sectomized rats [359].…”

“…The results of replacement by one or more pituitary principles in UNX rats show no significant effects from adrenotropin [23,359], thyrotropin [359], thyroxine [422] or prolactin [24]. The effects of somatotropin of varying degrees of purity tend to correlate inversely with the estimates of CRG in the untreated.…”

Serum and Urine Polyamines in Normal and in Short Children

“…Therefore, it has been proposed that polyamines mediate some growth-promoting actions of GH. That the biosynthesis of the polyamines is not under the sole control of GH, however, is demonstrated by the rises in ODC activity caused by other hormonal factors (2,16).…”

Blood Cell Polyamines in Children with Short Stature in Reference to Growth Hormone Activity

“…Thus, high activity of ODC and increased SPD/SP are present in tissues of rapidly growing young animals (8,9), in regenerating rat liver (lo), in compensatory or adaptive hypertrophy of renal and cardiac tissue (2,3), and in various tumors (8). Moreover, the circadian variation in renal ODC activity may be attributed to physiologic fluctuations in plasma GH levels in rats (14). Evidence for such physiologic association between GH activity and polyamine synthesis has also been found in human fetuses.…”